The present disclosure relates to an organic electroluminescent element (organic EL element) and a display, and more specifically to an organic EL element and a display which include a light-emitting layer including an anthracene derivative.
An organic EL element utilizing electroluminescence (hereinafter referred to as EL) of an organic material is configured by arranging an organic layer, which is formed by laminating an organic hole transport layer or an organic light-emitting layer, between an anode and a cathode, and the organic EL element attracts attention as a light-emitting element capable of emitting light with high luminance by a low-voltage DC drive.
FIG. 10 is a sectional view illustrating one configuration example of such an organic EL element. An organic EL element 51 is arranged on a transparent substrate 52 made of, for example, glass or the like, and is configured of an anode 53, an organic layer 54 and a cathode 55. The organic layer 54 has a configuration in which a hole injection layer 54a, a hole transport layer 54b, a light-emitting layer 54c and an electron transport layer 54d are laminated in order from the anode 53 side. Moreover, in addition to the above, there is an organic EL element configured by laminating the cathode 55, the organic layer 54 and the anode 53 in order from a substrate side.
In the organic EL element 51 with such a configuration, electrons injected from the cathode 55 and holes injected from the anode 53 are recombined in the light-emitting layer 54c, and light generated by recombination of the electrons and the holes is extracted through the anode 53 or the cathode 55.
In the organic layer 54 configuring the above-described organic EL element 51, the light-emitting layer 54c often uses a host material of an anthracene derivative to which a dopant (a guest material) as a luminescent center is added. The anthracene derivative has a higher electron-transport property than a hole-transport property. Therefore, in the light-emitting layer 54c using the anthracene derivative, an electron-hole recombination region is concentrated on the anode 53 side. Therefore, while high luminous efficiency is obtainable, electron leakage to the hole transport layer 54b easily occurs, and such electron leakage is one factor in a decline in life characteristics of the organic EL element 51.
Therefore, as an attempt to adjust a carrier balance in a whole element, there is disclosed an organic EL element with a configuration in which a layer with a high hole-transport property is arranged between the light-emitting layer 54c and the electron transport layer 54d (for example, refer to PTL 1).
Moreover, in the above organic EL element 51, to prevent a short between the anode 53 and the cathode 55 so as to reduce the occurrence of light emission failures, the organic layer 54 needs a certain or larger thickness. Typically, the thickness of the hole transport layer 54b exhibiting high mobility is increased to secure the thickness of the whole organic layer 54 (for example, refer to PTL 2). In addition, there is proposed an organic EL element with a configuration in which the electron transport layer 54d is doped with an active metal so as to have high mobility and the thickness of the electron transport layer 54d is increased (for example, refer to PTL 3).